The use of antimicrobial agents to reduce plaque/gingivitis as well as mouth odor has been recognized for many years. Included among references disclosing oral compositions containing antimicrobials are U.S. Pat. No. 3,937,805, Feb. 10, 1976 to Harrison; U.S. Pat. No. 3,937,807, Feb. 10, 1976 to Haefele; U.S. Pat. No. 4,080,441, Mar. 21, 1978 to Gaffar et al . ; U.S. Pat. No. 4,118,474, Oct. 3, 1978 to Gaffar et al.; U.S. Pat. No. 4,241,049, Dec. 23, 1980 to Colodney et al.; U.S. Pat. No. 3,925,543, Dec. 9, 1975 to Donahue; and U.S. Pat. No. 4,256,731, Mar. 17, 1981 to Curtis et al.
In addition to the materials mentioned in the patents set forth above, the prior art discloses the use of chlorine dioxide (ClO.sub.2) or chlorous acid (HClO.sub.2) liberating materials in oral products. One such reference is German Application 2329753, Dec. 13, 1973, to National Patent Development Corporation. The compositions in this reference are primarily alkaline but they may be acidic.
The German reference and other prior art disclosures which disclose chlorine dioxide or chlorous acid liberating materials in oral products do not suggest that the materials may cause tooth stain or how such stain may optimally be reduced.
The present inventors have discovered that the staining caused by chlorous acid compositions can be reduced by using citrate ions in combination with the chlorous acid and maintaining an appropriate pH.
Tooth stain is believed to be caused by the oxidation of amino acids on proteins (e.g., tryptophan, tyrosine) by chlorous acid, chlorine dioxide (or some other oxychlorine species formed along the chlorous acid/chlorine dioxide pathway) to fom brown-colored oxidation products which bind to the teeth. Citric acid may prevent tooth stain formation by reacting with these oxy chlorine species preventing reaction with amino acids or by preventing the binding of brown colored oxidation products to the tooth enamel . Citrate ions serve two purposes in the present invention: 1) liberation of chlorous acid/chlorine dioxide from the chlorite salt; and 2) prevention of tooth stain formation.
It is an object therefore to provide oral products which are effective against plaque and gingivitis.
It is a further object of the present invention to provide oral products/methods of use which are effective against plaque and gingivitis while not causing significant staining.
It is still a further object of the present invention to provide products utilizing a chlorous acid liberating agent as the active antiplaque-antigingivitis compound and citrate ions as the antistain material.
It is still a further object of the present invention to provide an effective method of treating plaque and gingivitis.
These and additional objectives will become readily apparent from the detailed description which follows. All percentages and ratios herein are by weight unless otherwise specified. Additionally, all measurements are made at 25.degree. C. unless otherwise specified.